(1)Regulatiory Mechanism of Tyrosine Hydroxylase--- We investigated the existence of the TH heterogeneity by RT-PCR analysis of the TH mRNAs from several species and analysis of the TH genes from some monkeys, to explore evolution of the TH gene. Also, we examined changes in the expression pattern of the human TH mRNA types in several disorders including Parkinson's disease and schizophrenia. Four kinds of the human TH isoform were expressed in E.coli, and purified to characterize their enzymatic properties. (2)Molecular Mechanism of the Neuron-Specific Gene Expression for Catecholamine- Synthesizing Enzymes---Analysis of the human TH gene promoter in transgenic mice has shown that tissue-specific expression of the TH gene requires the cis-element(s) located in the exon-intron region or 3'-downstream region of the gene in addition to its 5'-upstream promoter. Several transgenic analyzes have demonstrated that the 4-kb 5'-flanking region of the human DBH gene is sufficient for tissue-specific expression of the gene in both norepinephrine- and epinephrine-producing cells, and that the 2-kb 5'-flanking region of the human PNMT gene drives the transgene expression in adrenal gland chromaffin cells. Moreover, we have investigated activities of the alternative promoters which regulate tissue-specific expression of the human AADC gene. In transgenic mice carrying the 7.0-kb upstream region including the two alternative promoters of the AADC gene, the reporter gene expression was detected in the peripheral tissues including liver and kidney. (3) Functional Analysis of Catecholamine Neurons Using Transgenic Mice---We have succeeded in genetic conversion of catecholamine specificity from norepinephrine phenotype to epinephrine phenotype, by expressing PNMT under the control of the human DBH gene promoter in transgenic mice (DPN). In DPN mice, epinephrine release from the sympathetic neurons induced down-regulation of the adrenergic receptor subtype. A novel transgenic techni